T  A 


UC-NRLF 


LIBRARY 

OF    THE 

UNIVERSITY  OF  CALIFORNIA. 
das* 


HOW  TO  USE 


Portland  Cement 

From  the  German  of  L.  GOUNELU. 


Published  under  the  name  of  "  Das  Kleine  Cement- Buck" 

by  the  Association  of  German  Portland 

Cement  Manufacturers. 


Translated  by 

SPENCER  B.  NEWBERRV,  E.  M.  PH.  D., 

Actiug  Professor  of  Chemistry,  Cornell  University,  1887-1892. 

U.  S.  Commissioner  to  Paris  Exposition,  1889 

Judge,  Chicago  Exposition,  1893. 

Copyrighted  by  WILLIAM  SEAFERT, 
1899 


THIRD    EDITION    1904 


Price,  Fifty  Cents. 


CEMENT  AND  ENGINEERING  NEWS 
CHICAGO, 


IN    PREPARATION 


TREATISE;  OJNT 


Armored  Concrete  Constructions 

With  General  Applications  under  the  Various  Systems  in  use  in  the  United  States  and 
Europe,  with  numerous  illustrations  and  calculations. 

BY     E.     L.EE:     HEIDENREICW 

Member  American  Institute  Mining  Engineers  aud  Western  Society  of  Engineers. 
[COPYRIGHT  1903] 


SYNOPSIS    OF    CONTENTS. 

CHAPTER  I.     Abbreviated  history.  CHAP.  XIII.     General  notes  on  the  Relative 

CHAP.  II.     Cause  of  the  extraordinary  de-  j  and  Combined  Strength  of  Steel  and  Concrete 
velopment  of  Armored  Concrete.  CHAP.  XIV.     Calculation   of  Floor  Beams 

CHAP.  III.     Illustrated  applications  of  the     and  Girders, 
principal    systems    of     Floor     Constructions,  CHAP.  XV.     Calculation    of    Columns   and 

Beams,  Girders  and  Foundations.  !  Piers. 

CHAP.  IV.     Illustrated   application  of  the  I          CHAP.  XVI.   Calculation  of  Pipes,  Culverts 
principal  systems  of  Culverts,  Pipes  and  Tun-  j  Arches  and  Domes^ 


nel  Construction. 

CHAP.  V.     Tanks  and  Reservoirs. 

CHAP.  VI.  Cluster  Construction,  Grain 
Elevators,  Cement  and  other  storage. 

CHAP.  VII.  Retaining  Walls,  Docks  and 
Wharves. 


CHAP.  XVII.     Calculation    of    Tanks,    Re 
servoirs  and  Clusters. 

CHAP.    XVIII.      Calculation   of    Retaining 
i  Walls. 

CHAP.  XIX.     Calculation  of  Bridges. 
CHAP.  XX.     Practical    Details,   Tools   and 


Miscellaneous  Practical  De 


General  Conclusion. 
Index. 


CHAP.  VIII.    Arches  and  Domes.  |  Appliances. 

CHAP.  IX.     Bridges.  CHAP.  XXI.     Cost    of    Armored    Concrete 

CHAP.  X.     Stairs,  Grand  Stands.  Etc.  Construction. 

CHAP.  XI.     Manufactured  Articles,   Fence  j          CHAP.  XXII. 
Posts,  Smoke  Jacks,  Coffins,  Tubs,  Small  Cul      tails, 
vert  and  Sewer  Pipe,  etc.  CHAP.  XXIII. 

CHAP.  XII.     Application    of    Moulds    and  j         C  HAP.  XXIV7. 
Centers. 

THE  CEMENT  AND  ENGINEERING  NEWS  will  publish  this  treatise  on  "Armored  Concrete 
Constructions."  It  will  cover  from  500  to  700  pages  with  over  400  illustrations,  tables  and 
diagrams.  Abstracts  of  the  text  will  appear  monthly  up  to  the  date  of  publication.  The 
price  for  this  treatise  has  not  been  definitely  fixed,  but  orders  will  be  entered  ior  the  present 
at  $7,  C.  O.  D.,  on  delivery  of  the  book. 

to    The  Cement  and  Engineering  News 


Portland  Cement  Sidewalk 
Construction 

Based  upon  the  experience 
of  many  successful  side- 
walk contractors, 

— 

Compiled  by   P.    B.   BEERY 

Price,  50c  Delivered  by  Mail. 

Address : 

Cement  and  Engineering  News 

162  LaSalleSt.  CHICAGO,  ILL. 


Monier  Construction 


By  E.  Lee  Heidenreich 

Member  American  Institute  Mining    Engineers 
and  Western  Society  of  Engineers 

\  Treatise  on  the  use  of  Concrete  and  Steel 

Covering  Floors,  Arches,  Bridges,  Par- 
tition Walls,  Bridge  Floors,  Sewers, 
Conduits,  Tanks.  Reservoirs,  Grain 
Elevators,  Foundations  and  General 
Hydraulic  Engineering,  under  the 

Monier  System  of  Construction 

Numerous  Diagrams  and  Illustrations. 


Price  50  Cents,  Postpaid 

Cement  and  Engineering  News 

162  La  Salle  St.,  Chicago. 


HOW  TO  USE 


PORTLAND  CEMENT. 


From  the  German  of  L.  Golinelli. 

\\ 


Published  under  the  name  DAS  KLEINE  CEMENT-BUCH  by  the  Association 
German  Portland  Cement  Manufacturers. 


Translated  by  SPENCER  B.  NEWBERRY. 


[Copyrighted  by   WILLIAM  SEAFERT.] 


CHICAGO : 

CEMENT  AND  ENGINEERING  NEWS, 

1GOP. 


•-b' 


* 


f  . 


PREFACE. 


A  few  years  ago  a  very  important  and  useful  book, 
"Der  Portland-cement  und  seine  Anwendungen  im 
Bauwesen,"  (Berlin,  1892),  was  published  by  the  Asso- 
ciation of  German  Portland  Cement  Manufacturers. 
This  work  includes  the  best  information  obtainable  in 
reference  to  the  testing  and  uses  of  Portland  cement, 
and  contains  numerous  illustrations  showing  the  details 
of  important  examples  of  engineering  work  in  which 
cement  was  employed.  The  cordial  reception  given 
this  book  by  educated  engineers  led  the  association 
to  undertake  the  preparation  of  a  small  pamphlet  on 
the  same  subject,  intended  chiefly  for  the  use  of  con- 
tractors and  masons,  which  should  give  in  simple  and 
practical  form  the  results  of  the  best  experience  in  the 
use  of  Portland  cement.  This  pamphlet  has  lately  been 
issued  under  the  title  of  "  Das  Kleine  Cement-buch," 
by  the  publishers  of  the  Thonindusirie  Zeiiung.  Over 
22,000  copies  were  sold  in  Germany  during  the  past 
few  months,  and  a  new  edition  has  already  been  ordered. 

Germany  has  long  led  the  world  in  knowledge  of 
the  applications  of  cement,  and  most  of  our  best 
information  in  regard  to  methods  of  manufacture, 
testing  and  uses  of  cement  has  come  from  that  coun- 
try. A  full  translation  of  this  little  pamphlet,  repre- 
senting, as  it  does,  the  latest  German  thought  on  the 
subject,  will  therefore  doubtless  be  of  interest  to  Amer- 
ican cement  consumers. 

S.  B.  N. 
SANDUSKY,  O.,  March,  1899 


HOW  TO  USE  PORTLAND  CEMENT. 


Prom  the  German  of  L.  Golinelli. 

(Published  under  the  name  Daskleine  Cement-buch  by  the  Asso- 
ciation of  German  Portland  Cement  Manufacturers.) 

Translated  by  S.  B.  NEWBEBBY. 

It  is  an  established  fact  that  Portland  cement  is 
superior  to  all  other  hydraulic  materials,  natural  or 
artificial,  and  for  this  reason  it  is  widely  distributed 
throughout  the  world.  Its  use  would,  however,  be  far 
greater  if  the  knowledge  of  the  applications  and  meth- 
ods of  testing  of  cement  had  kept  pace,  during  the  past 
ten  years,  with  the  improvements  which  have  been 
made  in  quality  and  methods  of  manufacture.  Even 
in  sections  where  the  manufacture  of  Portland  cement 
has  been  extensively  and  successfully  developed,  and 
where  one  would  consequently  expect  to  find  a  certain 
amount  of  knowledge  of  the  subject,  a  correct  under- 
standing of  methods  of  testing  and  intelligent  use  of 
cement  is  often  painfully  lacking.  The  preparation  and 
use  of  cement  mortar,  as  practiced  in  many  cases  by 
masons  or  their  helpers,  is  not  onJy  imperfect  but 
wasteful.  Better  work  could  often  be  done  with  less 
material  if  careful  methods  were  used.  In  the  case  of 
Portland  cement  such  careful  methods  are  especially 
necessary  and  profitable,  and  if  they  were  followed  the 
common  complaint  that  Portland  cement  is  too  expens- 
ive would  soon  be  no  longer  heard.  Those  who  do 
intelligent  and  careful  work  have  for  a  long  time  recog- 
nized the  injustice  of  this  charge.  On  the  other  hand, 
it  is  undoubtedly  true  that  a  high-grade  material  like 


6        PBOPEBTIES  OF  PORTLAND  CEMENT. 

Portland  cement,  which  in  skillful  hands  may  be  use- 
fully and  economically  employed  for  an  immense  vari- 
ety of  purposes,  is  especially  liable  to  suffer  from  ignor- 
ance and  misuse. 

I.    PROPERTIES  OF  PORTLAND  CEMENT. 
DEFINITION  AND  MANUFACTURE. 

Portland  cement  is  a  material  which  hardens  in  the 
presence  of  water,  prepared  by  burning  at  a  sintering 
temperature  an  intimate  mixture  consisting  essentially 
of  lime  (or  carbonate  of  lime)  and  clay  in  certain  defin- 
ite proportions. 

The  raw  materials,  clay  and  carbonate  of  lime,  are 
ground  and  mixed  according  to  their  character  in  either 
the  wet  or  dry  way.  If  the  dry  process  is  used,  the 
mixed  materials  are  moistened  with  water  and  molded 
into  blocks.  In  the  wet  process  the  bricks  are  made 
from  the  wet  material  after  it  has  been  reduced  to  the 
proper  consistency.  After  drying,  the  bricks  of  cement 
material  are  burned  in  suitable  kilns  to  the  point  of 
sintering.  The  resulting  "  clinker "  is  ground  to  a  fine 
powder;  this  is  the  finished  cement. 

CHEMICAL  COMPOSITION. 

The  raw  materials  indicate  the  nature  of  the  constit- 
uents of  Portland  cement.  These  are  silica,  alumina, 
iron  oxide,  lime  and  a  small  amount  of  magnesia. 
Alkalies  and  sulphates  are  are  also  always  present,  and 
are  derived  from  the  raw  materials,  which  are  never 
found  pure  in  nature. 

The  presence  of  sulphuric  acid  (sulphate  of  lime)  is 
also  due  to  the  sulphur  in  the  fuel  employed,  and  to 
the  addition  of  a  small  amount  of  gypsum  (sulphate  of 
lime)  for  the  purpose  of  making  the  cement  slow-setting. 


CHEMICAL  COMPOSITION.  7 

The  composition  of  good  Portland  cement  usually 
varies  between  the  following  limits: 

Lame 58  to  65  per  cent 

Silica 20  to  26 

Alumina 7  to  14         •• 

Magnesia 1  to   3        «« 

Alkalies traces  to   3        •• 

Sulphuric  Acid traces  to   2         •* 

According  to  the  character  of  the  raw  material  used, 
each  manufacturer  determines  the  correct  composition 
of  his  product  within  the  above  limits,  and  this  com- 
position must  be  kept  uniform  by  constant  chemical 
analysis.  The  widespread  belief  that  defective  quality 
of  cement  is  due  to  bad  raw  materials  is  seldom  well 
founded;  the  fault  is  generally  due  to  incorrect  proporr 
tions  and  careless  manufacture. 

In  studying  the  qualities  of  Portland  cement,  the 
following  points  are  to  be  especially  noted : 

1.  Form  and  fineness  of  grain. 

2.  Color  and  specific  gravity. 

3.  Time  of  setting. 

4.  Hardening. 

5.  Strength. 

6.  Constancy  of  volume. 

7.  Hair  cracks  and  shrinkage  cracks. 

8.  Behavior  under  under  extreme  heat  and  cold. 

9.  Additions  and  adulterations. 

FORM  AND  FINENESS  OF  GRAIN. 

When  examined  under  the  microscope,  particles  of 
hydraulic  lime  have  a  more  or  less  rounded  form»~ 
Portland  cement,  on  the  other  hand,  shows  thin  leaf- 
lets of  shale-like  structure,  like  pounded  glass.  The 
high  quality  of  Portland  cement  is  in  part  due  to  this 
shale-like  character,  since  greater  density  of  mortar 


8  COLOR  AND   SPECIFIC  GRAVITY. 

results  from  the  greater  surface  of  contact  and  smaller 
proportion  of  voids  between  the  particles. 

As  to  fineness  of  grinding,  it  may  be  mentioned  that 
the  coarser  particles  of  cement  act  practically  like  sand. 
It  is  therefore  important  that  the  grinding  be  not  too 
coarse.  A  residue  of  not  more  than  5  per  cent  on  a 
sieve  of  75  meshes  to  the  linear  inch  may  fairly  be 
demanded.  The  finer  the  grinding,  the  more  sand  can 
be  used  with  the  cement.  It  should  be  remembered, 
however,  that  poor  cements,  especially  those  too  high 
in  clay  or  imperfectly  burned,  are  especially  easy  to 
grind  to  great  fineness.  Such  cements  may  be  gener- 
ally recognized  by  their  yellowish  color  and  the  spotty 
appearance  of  the  work. 

COLOR  AND  SPECIFIC  GRAVITY. 

The  color  of  Portland  cement  should  be  a  greenish 
gray;  a  yellowish  or  reddish  gray  tint  indicates  gener- 
ally an  inferior,  light-burned  product,  or  one  to  which 
under-burned  or  "  dusted  "  material  has  been  added. 

Portland  cement  has  a  high  specific  gravity,  a  quality 
which  contributes  to  its  high  value.  No  other  hydraulic 
material  has  so  high  a  specific  gravity,  or  yields  so 
dense  and  resistant  a  mortar.  The  specific  gravity  of 
Portland  cement  is  from  3.12  to  3.25. 

TIME  OF  SETTING. 

When  Portland  cement  is  mixed  with  a  suitable  qual- 
ity of  water,  a  plastic  paste  is  produced,  which  after  a 
time  becomes  hard.  The  change  from  a  semi-liquid  to 
a  solid  mass  is  called  setting,  and  the  time  required  for 
%is  change,  the  time  of  setting.  Cement  is  said  to  be 
set  when  it  resists  a  light  pressure  of  the  finger  nail  on 
the  surface. 


TIME  OF  SETTING.  9 

It  is  of  the  greatest  importance  to  know  the  time 
of  setting  of  a  cement  which  it  is  proposed  to  use,  since 
a  cement  which  has  become  set  and  has  been  again 
mixed  up  with  water  possesses  little  or  no  hydraulic 
energy.  The  mistake  of  mixing  "set"  mortar  anew 
with  water  occurs  only  too  often,  and  gives  rise  to  the 
unjust  complaint  that  the  cement  does  not  harden  or 
possesses  no  strength.  Great  care  should  therefore  be 
taken  to  mix  up  only  such  a  quantity  of  mortar  as  can 
be  conveniently  used  up  in  the  time  available;  this  can 
be  easily  managed  when  the  time  of  setting  is  known. 

Remnants  of  mortar  which  have  become  set  should  be 
discarded  and  must  under  no  circumstances  be  again 
worked  up  with  water. 

The  determination  of  the  time  of  setting  is  extremely 
simple,  and  may  be  made  by  any  mason  at  the  place 
where  the  cement  is  used.  The  best  method  is  as  fol- 
lows: 

The  cement  is  mixed  with  water  to  a  thick  paste, 
worked  one  to  two  minutes  with  a  spoon  or  trowel  and 
spread  out  in  the  form  of  a  pat  on  a  glass  plate.  This 
pat  should  be  about  one-half  inch  thick  in  the  middle 
and  thin  at  the  edges.  As  soon  as  the  surface  resists  a 
light  pressure  of  the  finger-nail  the  cement  is  set. 
Since  the  temperature  and  the  proportion  of  water 
used  are  of  great  influence  on  the  result,  it  is  best  to 
have  the  cement  and  water  at  the  ordinary  temperature 
of  60  to  70  degrees,  and  to  use  not  more  than  30  to  32 
per  cent  of  water.  The  water  must  be  clean.  The  pat 
should  be  protected  from  sunshine  and  drafts  of  air. 

It  is  in  the  power  of  the  manufacturer  to  produce 
either  quick-setting  or  slow-setting  cement,  as  may  be 
required.  A  cement  which  requires  two  hours  or  longer 
to  set  is  called  slow-setting.  Such  cement  is  preferable 


10  HARDENING. 

to  that  which  sets  quickly,  on  account  of  its  greater 
strength.  Quick-setting  cement  is  used  only  for  cer- 
tain special  purposes.  Slow-setting  cement  can  be 
made  to  set  more  quickly  by  using  warm  water,  and 
also  by  limiting  the  water  used  to  the  smallest  possible 
quantity.  Among  the  substances  which  modify  the 
time  of  setting  may  be  mentioned: 

Potash  and  soda,  which  hasten  the  setting.  Sulphates 
and  calcium  chloride,  which  retard  the  setting. 

In  all  cases  the  consumer  will  do  well  to  notify  the 
manufacturer  what  time  of  setting  is  desired,  also  for 
what  purpose  the  cement  is  to  be  used.  In  this  way 
many  unjust  complaints  in  regard  to  quality  and  many 
unnecessary  expenses  may  be  avoided. 

HARDENING. 

The  set  cement  is  capable  of  hardening,  either  in 
water  or  in  air,  and  in  a  short  time  will  acquire  a  high 
degree  of  strength.  The  processes  of  setting  and  hard- 
ening should  not  be  confused.  The  latter  begins  at  the 
point  where  the  former  ceases,  and  continues  up  to  the 
highest  strength  which  the  cement  attains  after  the 
lapse  of  many  years, 

As  to  the  nature  of  the  hardening  process,  to  account 
for  which  various  theories  have  been  advanced,  it  need 
only  be  here  stated  that  the  hardening  consists  in  chem- 
ical combination  with  water  taking  place  under  certain 
physical  conditions.  Among  the  most  important  of 
these  conditions  are  rest  during  the  setting  and  protec- 
tion from  too  rapid  drying  out.  The  latter  point  can 
not  be  too  strongly  insisted  upon,  If  the  cement  is 
deprived  of  the  necessary  water  it  can  never  reach  its 
full  hardness. 


STRENGTH.  11 

Portland  cement  attains  within  a  few  days  a  high 
degree  of  strength. 

In  the  use  of  cement  for  building  purposes,  compres- 
sion strength  is  the  quality  generally  required.  Cement 
is,  however,  generally  tested  only  for  tensile  strength, 
owing  to  the  fact  that  the  tests  of  tensile  strength  can 
be  made  much  more  quickly,  simply  and  cheaply  than 
those  of  compression.  There  is  also  a  definite,  (though 
by  no  means  exact)  relation  between  the  two  tests,  the 
compression  strength  being  generally  from  8  to  12 
times  the  tensile  strength. 

The  German  official  standards  for  Portland  cement 
require  that  a  mixture  of  one  part  cement  with  three 
parts  normal  sand  shall  show  a  tensile  strength  at  28 
days  of  at  least  227  Ibs.  per  sq.  in. 

It  is  by  no  means  simple,  however,  to  make  tensile 
strength  tests  in  such  a  manner  as  to  give  reliable 
results.  Complaints  in  regard  to  the  quality  of  cement 
are  often  due  entirely  to  faulty  testing.  In  the  prepar- 
ation of  briquettes,  the  temperature  and  quantity  of  the 
water  used,  the  character  of  the  sand  employed,  and 
the  thoroughness  with  which  the  mortar  is  worked,  are 
of  immense  influence  on  the  results.  The  strength  will 
generally  be  greater  the  less  water  is  used;  nevertheless 
it  is  always  necessary  to  use  such  a  quantity  of  water 
that  it  shall  show  itself  on  the  surface  of  the  briquette 
on  tamping  it  into  the  mold,  Long  and  vigorous  work- 
ing of  the  mortar  increases  its  strength.  In  extensive 
building  operations  the  use  of  mixing  machines,  especi- 
ally pans  with  edge  runners,  is  therefore  highly  advan- 
tageous. 

CONSTANCY  OF  VOLUME  AND  CRACKING. 

Strictly  speaking,  there  is  no  such  thing  as  constancy 
of  volume,  either  in  the  case  of  mortar  or  stone,  since 


12      CONSTANCY  OF  VOLUME  AND  CBACKING. 

heat  and  cold,  wetting  or  drying,  modify  the  volume 
more  or  less.  Portland  cement  also  suffers  changes  of 
volume  on  hardening  in  water  or  in  air.  In  the  case  of 
good  Portland  cement,  however,  these  changes  are 
extremely  small  and  much  less  than  those  which  occur 
in  different  kinds  of  stone.  Bad  cements,  on  the  other 
hand,  may  show  the  dangerous  quality  of  cracking  or 
swelling.  This  shows  itself  in  a  strong  expansion, 
which  destroys  the  cohesion  of  the  mortar  and  may 
cause  its  total  destruction.  Cement  which  swells  badly, 
if  laid  between  retaining  walls,  shows  an  immense 
power  of  expansion,  even  to  the  extent  of  forcing  out 
the  stones  of  the  masonry. 

The  swelling  does  not  show  itself  until  after  the  set- 
ting. The  worse  the  fault  is  the  sooner  it  will  appear, 
It  shows  itself,  also,  sooner  in  water  than  in  air.  In 
pats  of  cement  kept  under  water  this  defect  is  to  be 
noticed  in  the  appearance  of  fine  net-like  cracks,  or  in 
worse  cases  in  curving  of  the  pats  and  the  appearance 
of  cracks  around  the  edges.  It  is  characteristic  of 
expansion  cracks  that  they  run  from  the  edges  toward 
the  center  of  the  pat  and  are  widest  at  the  edges  and 
narrower  toward  the  center.  These  expansion  cracks 
should  not  be  confused  with  shrinkage  cracks,  mention 
of  which  will  be  made  later. 

The  swelling  of  cement  is  always  due  to  defects  in 
manufacture.  These  are: 

1.  Faulty  composition  of  the  raw  material,  especi- 
ally too  high  a  proportion  of  lime. 

2.  Imperfect  preparation  of  the  raw  material. 

3.  Imperfect  burning  of  the  clinker. 

4.  Too  high  proportion  of  sulphate  or  magnesia. 
According  to  the  German  official  requirements,   a 

cement  is  considered  to  be  constant  in  volume  if  a  pat, 


SHRINKAGE-CRACKS   AND   HAIR-CRACKS.  13 

kept  28  days  under  water,  remains  perfectly  flat  and 
free  from  cracks.  Swelling,  due  to  too  much  lime, 
shows  itself  in  this  test  with  certainty  within  a  few 
days  or  weeks.  Cement  containing  too  much  magnesia, 
howeyer,  and  burned  to  the  point  of  sintering,  shows 
noticeable  expansion  only  after  the  lapse  of  long  peri- 
ods, extending  even  to  several  years.  Only  chemical 
analysis,  or  the  guarantee  of  the  manufacturer,  can 
afford  protection  against  the  danger  of  expansion  from 
excess  of  magnesia.  Experience  has  shown  that  the' 
presence  of  magnesia  up  to  3  per  cent  is  entirely  harm- 
less. 

In  conclusion,  two  other  peculiar  appearances  may 
be  mentioned  which  are  often  erroneously  considered 
to  indicate  swelling  of  the  cement. 

It  is  sometimes  noticed  that  pats  of  neat  cement, 
left  in  air,  lose  considerably  in  strength,  and  after  a 
certain  time  become  soft  or  friable,  while  similar  pats 
kept  in  water  are  faultless  in  all  respects.  This  is  espe- 
cially liable  to  occur  in  the  case  of  pats  made  very  wet 
and  allowed  to  dry  out  immediately  after  setting.  If, 
on  the  other  hand,  the  pats  are  kept  moist  during  the 
first  stages  of  hardening,  this  defect  is  not  developed. 

Cracks,  similar  to  those  produced  by  swelling,  are 
also  produced  when  pats  or  briquettes  are  placed  in 
water  too  soon,  or  before  the  setting  is  complete.  To 
prevent  this  the  official  requirements  specify  that  test- 
pieces  shall  be  kept  24  hours  in  moist  air  before  placing 
in  water. 

SHRINKAGE-CRACKS  AND  HAIR-CRACKS. 

Portland  cement  mortar  without  sand,  exposed  to  the 
air,  diminishes  in  volume.  If  the  drying  takes  place 
gradually  and  uniformly,  as  in  a  closed  room,  the 
cement  shows  no  defects.  Too  rapid  drying,  in  draughts 


14  RESISTANCE  TO  WEATHER. 

of  air  or  in  sunshine,  without  the  precaution  of  keeping 
the  cement  moist,  causes  so-called  shrinkage-cracks. 
These  may  be  distinguished,  in  pats  of  cement,  from 
expansion-cracks  by  the  fact  that  they  appear  during 
the  setting  and  show  themselves  as  irregular  curved 
lines  extending  over  the  middle  of  the  pat.  As  already 
stated,  the  formation  of  shrinkage  cracks  is  due  to 
faulty  use  of  the  cement,  and  has  practically  nothing  to 
do  with  its  quality.  Very  finely  ground  cements  are, 
moreover,  more  likely  to  show  hair-cracks  than  those 
which  are  more  coarsely  ground. 

Hair-cracks  appear  as  fine  lines  on  cement  work 
which  has  stood  some  time.  They  are  especially  to  be 
noticed  on  cement  which  has  lain  in  the  open  air,  and 
are  due  to  frequent  changes  between  wet  and  dry  con- 
ditions. Hair-cracks  and  shrinkage-cracks  occur  chiefly 
when  pure  cement  or  mortar  too  rich  in  cement  is  used. 
They  may  be  certainly  avoided  by  the  addition  of  suffi- 
cientsand  and  suitable  treatment  of  the  work. 

RESISTANCE  TO  WEATHER  AND  BEHAVIOR  UNDER  EXTREME 
HEAT  AND  COLD. 

Mortar  made  from  pure  cement  is,  strictly  speaking, 
not  weatherproof,  owing  to  its  tendency  to  form  shrink- 
age-cracks and  hair-cracks.  Eepeated  expansion  and 
shrinkage  increases  the  number  and  size  of  these  cracks, 
until  finally  under  the  action  of  water  and  frost  the 
cement  breaks  to  pieces.  Complete  weather-resisting 
qualities  can  be  given  to  cement  mortar  only  by  the 
the  addition  of  sand.  One  part  sand  to  one  part  cement 
will  be  found  sufficient. 

The  temperatures  which  are  reached  in  warm,  or 
even  hot,  climates  have  no  bad  influence  on  the  harden- 
ing of  Portland  cement.  The  only  precaution  necessary 


BEHAVIOR  UNDER  EXTREME  HEAT  AND  COLD.  15 

is  to  see  that  the  water  necessary  for  hardening  is  not 
removed  too  soon;  or,  in  other  words,  that  the  work  is 
kept  sufficiently  moist  during  the  earlier  stages  of  hard- 
ening. Even  the  temperature  of  boiling  water  is  harm- 
less to  the  strength  of  Portland  cement,  and  a  heat  of 
400  degrees  to  500  degrees  F.  may  be  borne  without  in- 
jury. At  a  red  heat  it  becomes  soft  and  friable.  Never- 
theless it  has  been  proved  by  long  experience  with 
Portland  cement  concrete  that  this  material  shows  a 
high  degree  of  strength  and  safety  when  exposed  to  fire. 
Portland  cement  is  less  affected  by  frost  than  any 
other  hydraulic  material,  If  the  cement  is  once  fully 
set  it  may  be  exposed  to  strong  freezing  without  any 
ill  effect.  It  is  only  during  the  setting  that  injury  can 
take  place,  and  this  is  chiefly  to  be  feared  in  case  the 
mortar  was  made  too  wet,  so  that  the  freezing  of  the 
water  forces  the  mass  asunder.  If  water  is  sparingly 
used,  masonry  and  concrete  work  may  be  done  in 
extremely  cold  weather  with  good  results.  It  must  be 
remembered,  however,  that  the  setting  and  hardening 
of  cement  are  much  delayed  by  cold.  Cement  work 
done  in  freezing  weather  shows,  therefore,  but  little 
strength  at  first,  but  finally  reaches  its  normal  hardness. 
Addition  of  salt  to  mortar  in  cold  weather  is  generally 
to  be  avoided  on  account  of  the  unsightly  efflorescences 
which  often  result.  It  is  better,  when  work  in  extreme 
heat  or  cold  cannot  be  avoided,  to  warm  the  water 
and  sand  used  and  to  reduce  the  water  to  the  small- 
est possible  quantity  in  order  to  hasten  the  setting  of 
the  mortar.  If  care  is  taken  to  allow  no  free  water  to 
separate,  or  that  any  excess  of  water  is  absorbed  by  dry 
stone,  there  is  nothing  to  be  feared  even  from  extreme 
cold.  Surface  plastering  with  cement  should,  how- 
ever, not  be  attempted  in  freezing  weather. 


16  ACTION  OF  SEA  WATEB. 

On  mixing  cement  with  sea  water  the  setting  is 
delayed  and  decreased  strength  results.  This  is  chiefly 
due  to  the  action  of  the  magnesium  sulphate  and  chlor- 
ide of  the  sea  water  on  a  portion  of  the  cement;  the 
hardening  value  of  this  part  is  therefore  lost  and  the 
strength  attained  is  less  than  with  the  use  of  fresh 
water.  One  might  suppose  that  this  action  of  the  sea 
water  salts  would  cause  the  strength  of  the  cement  to 
continue  to  fall  off  and  that  the  work  would  finally 
fall  to  pieces.  This  is,  however,  not  the  case,  owing  to 
the  fact  that  the  penetration  of  the  sea  water  into  the 
mass  is  prevented  by  the  great  and  constantly  increasing 
density  of  the  Portland  cement  mortar.  A  deposit  of 
magnesia  is  also  formed  in  the  pores  of  the  mass,  and 
gives  further  protection  against  the  entrance  of  the 
sea  water.  Portland  cement  is  therefore  unequalled 
for  marine  constructions.  In  all  cases  in  which  this 
work  has  been  intelligently  done  Portland  cement  con- 
crete has  fulfilled  all  requirements  most  satisfactorily. 
In  work  exposed  to  sea  water  it  is  of  the  highest 
importance  to  give  the  concrete  as  dense  and  close- 
grained  a  surface  as  possible,  since  only  such  a  surface 
is  capable  of  permanently  resisting  the  chemical  action 
of  the  salt  water  and  the  mechanical  force  of  the  waves. 

Portland  cement  is  especially  suitable  for  work  of 
this  kind,  since  uniform  tests  of  tensile  and  compres- 
sion strength  are  a  guarantee  of  a  uniform  material 
which  can  safely  be  relied  upon.  This  is  by  no  means 
true  in  the  case  of  puzzuolana  cements,  so-called  slag 
cements  and  hydraulic  limes,  which  are  often  of  very 
variable  quality. 

ADDITIONS  AND  ADULTEBATIONS. 

Substances  added  to  Portland  cement  may  be  divided 
into  those  which  are  intended  to  give  it  certain  valuable 


ADDITIONS  AND  ADULTERATIONS.  17 

qualities,  and  others  which  are  added  for  the  purpose 
of  fraud.  In  the  first  group  are  found  gypsum  and 
coloring  matters. 

The  addition  of  gypsum  (sulphate  of  lime)  which 
should  not  exceed  2  per  cent,  is  made  for  the  purpose 
of  causing  naturally  quick-setting  cements  to  set  more 
slowly.  In  this  way  the  quality  of  the  cement  is 
improved  and  its  strength  increased.  Additions  of  a 
higher  proportion  of  gypsum  are  not  admissable,  as  it 
tends  to  cause  swelling. 

Coloring  matters  are  sometimes  added  to  cement  in 
order  to  make  it  suitable  for  decorative  purposes. 
Mineral  colors  are  practically  always  used.  To  give  the 
cement  a  somewhat  darker  tint,  especially  for  use  in 
making  cement  wares,  a  few  per  cent  of  lamp-black 
is  added.  Nearly  all  coloring  matters  reduce  the 
strength  of  the  cement;  ultra-marine,  however,  in  small 
quantities,  increases  it.  The  red  iron  oxide  of  com- 
merce, often  used  to  produce  a  red  color,  frequently 
contains  a  considerable  amount  of  sulphuric  acid,  and 
may  cause  swelling.  Care  should  be  taken  in  the 
choice  of  the  coloring  matters  employed. 

In  regard  to  the  production  of  white  Portland  cement 
it  may  be  said  that  this  has  not  hitherto  proved  success- 
ful, on  account  of  impurities  contained  in  the  raw 
materials  or  derived  from  the  fuel.  The  so-called 
white  cements  of  commerce  are  for  the  most  part 
inferior  products  which  do  not  deserve  the  name  of 
Portland  cement.  In  consequence  of  its  gray  color, 
Portland  cement  cannot  be  made  white  by  the  addition 
of  pigments. 

From  fraudulent  and  avaricious  motives,  blast  furn- 
ace slag,  limestone,  shale,  basalt,  ashes,  sand,  etc,,  are 
added  to  cement.  These  are  simply  adulterations, 


18  PACKING  AND  WEIGHT.— SEASONING. 

which  always  injure  the  quality  of  the  product.  These 
substances  may  be  more  or  less  easily  detected,  and 
their  use,  in  consequence  of  the  close  watch  kept  by 
the  association  upon  the  product  of  its  members,  has  of 
late  practically  ceased. 

II.    USE  OF  PORTLAND  CEMENT. 
PACKING  AND  WEIGHT. 

(American  weights  are  here  substituted  for  the  German  weights 
given  in  the  original  pamphlet.— TBANSLATOB.) 

Portland  cement  is  packed  in  barrels  and  sacks.  The 
barrel  is  of  400  Ibs.  weight  and  contains  380  Ibs.  (about 
3J  cubic  ft,)  of  cement.  Sacks  are  generally  one-fourth 
barrel,  or  95  Ibs.  Since  empty  barrels  and  sacks  are 
received  by  the  manufacturer  at  a  certain  price,  care 
should  be  taken  to  preserve  them  in  an  orderly  manner. 
Empty  sacks  are  most  conveniently  returned  in  bundles 
of  ten  each. 

Barrels  and  sacks  should  be  marked  by  the  manu- 
facturer with  name,  trade-mark  and  gross  weight  of 
package.  Loss  by  sifting  out  and  variations  from 
standard  weight  to  the  amount  of  2  per  cent  are  allow- 
able. 

STORAGE  (SEASONING)  OF  CEMENT. 

Storage  of  cement  improves  its  quality.  If  well  pro- 
tected and  kept  dry  the  cement  gains  in  strength  and 
becomes  more  slow-setting  and  more  constant  in  vol- 
ume. This  so-called  seasoning  results  from  the  action 
of  the  moisture  and  carbonic  acid  of  the  air.  At  the 
same  time,  owing  to  the  disintegration  of  the  coarser 
grains,  the  cement  increases  in  fineness.  If,  however, 
cement  is  stored  in  a  damp  place  it  becomes  caked, 
lumpy,  partially  set,  and  finally  worthless.  Dealers 
should  keep  this  in  mind  and  give  close  atten- 


CHOICE  OF  CEMENT.  19 

tion  to  the  choice  of  a  suitable  place  for  storage. 
Portland  cement  bears  long  storage  well,  and  even  if 
packed  in  sacks  may  be  safely  kept  in  a  dry  place  for 
many  months. 

If  fresh,  insufficiently  seasoned  cement  is  packed,  an 
increase  of  volume  takes  place  on  long  storage,  and  if 
the  barrels  are  too  completely  filled  or  the  hoops  too 
strongly  driven  the  hoops  may  be  broken  or  the  staves 
bent  out.  This  may  occur  with  faultless  cements,  and 
has  nothing  to  do  with  so-called  swelling  or  cracking. 

CHOICE  OF  CEMENT  AND  CONCRETE  MATERIALS. 

Quick-setting  cements  are  used  for  work  exposed  to 
leaching  water,  also  for  plastering  and  casts.  For 
all  other  purposes  slow-setting  cement  is  preferable. 
Neat  Portland  cement  is  rarely  used  for  mortar,  and 
only  in  case  the  work  is  to  remain  constantly  under 
water  or  in  damp  earth.  In  other  cases  more  or  less 
sand  must  be  used  to  prevent  shrinkage-cracks  and 
produce  a  weatherproof  mortar. 

The  character  of  the  sand,  gravel  and  stone  used  has 
great  influence  on  the  strength  of  the  work.  The  sand 
must  be  sharp  and  pure ;  if  it  contains  clay  this  must 
be  removed  by  repeated  washing.  Very  fine  sand  is 
generally  objectionable;  the  best  results  are  obtained 
with  a  graded  sand,  consisting  of  grains  of  various 
sizes,  from  fine  to  coarse.  Stone  and  gravel  for  con- 
crete must  also  be  naturally  clean  or  well  washed,  and 
must  not  be  soft  or  chalky.  Only  clean  water,  free 
from  mud,  should  be  used  for  mixing  cement  mortar. 

PREPARATION  AND  USE  OF  MORTAR. 

If  good  results  are  to  be  obtained  with  Portland 
cement  great  care  must  be  taken  in  the  preparation  of 
the  mortar.  If  vessels  which  have  been  used  for  lime 


20         PREPARATION  AND  USE  OF  MORTAR. 

or  contain  set  cement  are  employed  these  must  be 
well  cleaned  before  use.  As  cement  and  sand  are 
mixed  in  proportions  by  measure,  it  is  a  good  plan 
to  provide  measuring  vessels  corresponding  to  the  vol- 
ume of  the  cement  packages.  The  necessary  figures 
are  given  in  a  previous  paragraph  under  "Packing  and 
Weight."  Guess-work  mixtures  should  never  be  made, 
for  such  methods  not  only  give  mortar  of  varying  com- 
position, but  also  cause  unnecessary  waste  of  cement. 

The  proportion  of  sand  to  be  used  varies  with  the 
character  of  the  worki;  1  to  2  parts  sand  to  1  cement 
are  used  only  for  work  requiring  extraordinary  strength, 
great  resistance  to  wear,  or  impermeability  to  water;  3 
to  4  parts  sand  to  1  part  cement  are  employed  for 
ordinary  weatherproof  plastering,  building  mortar, 
foundations,  artificial  stone,  etc. 

More  or  less  water  should  be  taken  according  to  the 
rate  of  setting  of  the  cement,  conditions  of  temperature, 
and  kind  of  work  in  view.  As  a  general  rule  as  little 
water  as  possible  should  be  used,  and  the  mortar  made 
plastic  by  prolonged,  vigorous  mixing.  For  the  prep- 
aration of  mortar  the  measured  quantity  of  sand  is 
spread  out  and  the  correct  amount  of  cement  scat- 
tered evenly  over  it;  the  two  materials  are  then  thor- 
oughly mixed  together.  The  necessary  quantity  of 
water  is  then  strongly  and  thoroughly  worked  into  the 
mass. 

One  of  the  chief  rules  in  preparing  mortar  is  that 
cement  which  has  become  set  should  never  be  worked 
up  anew  with  water.  For  this  reason  no  more  mortar 
should  be  mixed  at  one  time  than  can  be  used  before 
the  setting  begins.  Mortar  which  has  become  set  and 
is  again  made  plastic  with  water  will  never  gain  its 
normal  hardness.  Another  important  point  is  that  the 


CEMENT-LIME    MORTAR.  21 

brick  or  stone  used  for  building  must  be  thoroughly 
wetted  before  being  laid  up  with  cement  mortar.  The 
work  should  also  be  kept  damp  for  a  considerable  time 
after  it  is  finished,  in  order  that  the  mortar  may  reach 
its  full,  stone-like  hardness.  The  common  practice  of 
wetting  bricks  just  before  use  by  sprinkling  with  water 
from  the  mason's  brush  is  quite  insufficient.  The  bricks 
should  be  kept  under  water,  in  a  vessel,  until  thoroughly 
saturated,  and  a  stiff  mortar  used,  in  order  that  the 
brick  should  not  be  displaced  after  laying. 

CEMENT-LIME    MORTAR. 

There  are  many  kinds  of  work  which  require  a  quick- 
hardening  mortar,  but  for  which  the  great  strength  of 
a  mixture  of  1  cement  with  1  to  4  of  sand  is  unneces- 
sary. The  cost  of  such  mortar  is  also,  for  many  pur- 
poses, too  high.  A  mixture  of  cement  with  5  or  more 
parts  sand  would  give  abundant  strength,  but  such 
mortar  works  too  "  short "  and  adheres  too  imperfectly 
to  the  brick  or  stone ;  it  cannot,  therefore,  safely  be  used. 

In  such  cases  the  addition  of  slaked  lime  or  hydraulic 
lime  will  correct  the  faults  of  poor  mixtures  of  cement 
and  sand,  and  will  produce  a  cheap  mortar,  suitable 
for  a  great  variety  of  uses.  The  addition  of  slaked 
lime  allows  the  full  advantage  to  be  obtained  from  the 
use  of  good  Portland  cement,  and  makes  it  possible  for 
this  material  to  compete  in  price  with  cheaper  hydraulic 
materials.  Used  in  this  manner,  Portland  cement  may 
be  employed  with  economy  for  the  most  ordinary  pur- 
poses. The  advantages  of  Portland  cement  lime  mortar 
are  its  cheapness  in  comparison  with  other  hydraulic 
materials,  it  rapid  hardening,  marked  hydraulic  prop- 
erties, great  strength  on  exposure  to  air,  and  remark- 
able resistance  to  weather. 


22       PORTLAND  CEMENT  MOBTAB  IN  WATEB  AND  AIB. 

The  following  mixtures  for  cement-lime  mortar  have 
been  found  by  experience  to  be  most  suitable: 
Cement  1,    sand  5,         lime  paste    %. 

1,       "    6  to  7,     "        "      1 
"         1,       "    8,  "        "      \% 

"          1,        "  10,  "        "      2 

The  above  proportions  are  to  be  taken  by  measure. 
Hydraulic  lime  may  be  used  in  place  of  ordinary  slaked 
lime. 

Cement-lime  mortar  is  prepared  by  making  a  dry 
mixture  of  the  required  quantities  of  cement  and  sand; 
milk  of  lime  is  then  made  with  the  necessary  quanti- 
ties of  lime  paste  and  water,  and  this  milk  of  lime 
thoroughly  mixed  and  worked  in  with  the  mixture  of 
cement  and  sand. 

The  great  advantages  of  cement-lime  mortar  for  a 
multitude  of  purposes  deserve  to  be  more  widely 
recognized  than  they  are  at  present. 

POBTLAND  CEMENT  MOBTAB  IN  WATEB   AND  IN  AIB. 

On  account  of  its  remarkable  hydraulic  properties, 
great  strength,  and  durability,  Portland  cement  mortar 
gives  excellent  results  both  in  water  and  in  air.  The 
first  essential  to  success  is,  however,  that  the  mortar 
should  be  prepared  and  used  suitably  and  intelligently 
for  the  special  purpose  in  view.  For  work  to  be 
exposed  to  water,  care  must  be  taken  to  produce  as 
dense  and  impenetrable  a  surface  as  possible;  this  may 
be  accomplished  by  mixing  the  materials  in  suitable 
proportions.  Ornaments,  casts,  etc.,  which  are  to  be 
exposed  to  weather  must  never  be  made  from  pure 
cement;  the  same  may  be  said  of  architectural  artificial 
stone  work.  A  certain  proportion  of  sand  must  always 
be  added, 


WATER-TIGHT   MOBTAB.  23 

In  the  preparation  of  water-tight  mortar  it  should  be 
remembered  that  the  richer  the  mixture  is  in  cement 
and  the  longer  the  mortar  hardens  the  greater  will  be 
it  impermeability  to  water.     The  reason  of  this  is  that 
in  the  process  of  hardening  the  mortar  becomes  con- 
stantly more  dense,   and  the  pores  gradually  close. 
The  porosity  of  mortar  is  the  greater,  the  thinner  the 
layer  employed  and  the  higher  the  proportion  of  sand 
used,     Coarse  sand,  also,  gives  a  more  porous  mortar 
than  fine  sand.     For  a  coating  f  to  £  of  an  inch  in 
thickness  which  requires  to    be    immediately    water- 
proof,  the  following  mixtures  are  recommended: 
Cement,  1,  sand     (not  too  coarse),  1 
tt       1,    "    1,      lime    paste         K 
u       1,    «    3,         "  "  1 

"       1,    "    5,         "  "  1# 

u        1,    «    6,         "  "  2 

Which  of  these  mixtures  is  to  be  employed  depends 
on  the  nature  of  the  work.  By  the  addition  of  gravel 
or  broken  stone  to  the  above  mixtures  water-tight  con- 
crete is  obtained.  From  motives  of  economy,  however, 
it  is  customary  to  make  only  the  surface  of  the  concrete 
of  water-tight  composition. 

CEMENT   PLASTERING  AND   PAINTING. 

Experience  has  shown  that  cement  plastering  on  walls 
and  cornices,  even  when  made  with  faultless  material,  is 
not  always  permanent.  Sometimes  the  surface  scales 
off  in  thin  layers;  in  other  cases  blisters  form  and  crack, 
or  the  whole  layer  of  plastering  may  separate  from  the 
wall  and  fall  off.  In  all  such  cases  the  work,  and  not 
the  cement,  is  at  fault.  If  walls  are  to  be  plastered  with 
cement  mortar  it  is  indispensable  that  the  surface  be 
previously  thoroughly  cleaned  from  dust,  dirt  or  lime- 
mortar,  washed  and  repeatedly  wetted.  If  the  wetting 


24  CEMENT  PLASTERING  AND  PAINTING. 

is  insufficient  the  dry  stone  or  brick  take  away  from 
the  cement  the  water  necessary  for  hardening;  if  this 
happens  the  mortar  adheres  badly  and  never  reaches 
its  proper  hardness.  Wall-plastering  which  is  exposed 
to  weather  should  never  be  made  very  rich  in  cement 
for  fear  of  the  formation  of  shrinkage  cracks.  The 
more  sand  is  used,  provided  the  necessary  strength  is 
obtained,  the  better  the  plastering  will  resist  the 
weather.  Fine  sand  should  be  used,  and  for  the  pur- 
pose of  avoiding  hair-cracks  and  shrinkage  cracks  it  is 
best  to  finish  the  surface  with  a  felt  polisher  instead  of 
a  trowel  or  steel  tool. 

Cement  plastering  must  be  kept  moist  and  pro- 
tected from  wind  and  sun.  This  work  can  be  done 
most  advantageously  in  spring;  frost  should  be  espec- 
ially avoided.  Some  sands  contain  little  particles  of 
coal  which  are  scarcely  visible  to  the  eye;  these  may 
have  a  very  bad  effect  on  the  appearance  of  the  work. 

Cement  work  which  is  to  be  painted,  either  on  account 
of  hair-cracks  or  efflorescences  derived  from  the  alkal- 
ies and  lime  of  the  cement,  or  from  any  other  cause, 
must  be  fully  hardened  and  thoroughly  dry.  It  is 
prudent  to  let  the  work  stand  a  year  before  oil  paint  is 
applied.  To  insure  the  durability  of  the  painting 
several  methods  may  be  used. 

1.  The  surfaces  are  repeatedly  brushed  over  with 
dilute  sulphuric  acid  (1  part  strong  acid  to  100  parts 
water),  and  allowed  to  dry  before  the  paint  is  applied. 

2.  The  surfaces  are  repeatedly  and  carefully  washed 
with  water,  then  after  8  days,  saturated  twice  with  lin- 
oleic  acid  (to  be  had  from  any  druggist).     After  a  few 
days,  when  the  surface  has  grown  hard,  the  oil  paint  is 
applied. 

3.  An  excellent  preparatory  coating  for  oil  paint  is 


CONCRETE.  25 

a  solution  of  common  water-glass  in  3  or  4  parts  water. 
After  two  applications  the  surface  is  washed  with  water; 
after  a  short  time  the  water-glass  is  again  applied. 
When  dry  the  paint  can  be  used. 

Even  oil  paint  is,  however,  often  of  slight  durability 
when  exposed  to  weather.  For  work  of  great  perman- 
ence the  patent  process  of  Dr.  Golinelli,  Koch  and 
Adamy  of  Darmstadt,  for  preparation  of  cement  work 
for  stereochromatic  painting,  may  here  be  mentioned. 

CONCRETE. 

One  of  the  most  important  uses  of  Portland  cement 
is  in  the  making  of  concrete.  This  is  a  mixture  of 
cement  with  sand  and  gravel  or  broken  stone,  with  the 
addition  of  the  necessary  water.  To  obtain  good  ad- 
hesion of  the  materials,  the  water,  sand  and  stone  must 
all  be  clean;  in  some  cases  washing  of  these  materials 
may  be  necessary. 

The  gravel  or  stone  used  must  be  at  least  equal  in 
hardness  to  the  cement  mortar.  Good  gravel,  basalt  or 
hard  lime  stone  are  most  suitable;  soft  sandstone  or 
broken  brick  are  to  be  avoided.  The  stone  should  not 
be  above  egg  size.  The  proportions  to  be  used  depend 
on  the  nature  of  the  work.  When  once  determined 
they  should  be  rigidly  adhered  to.  For  the  preparation 
of  concrete,  the  cement  and  sand  are  well  mixed 
together  on  a  dry  platform ;  enough  water  is  then  mixed 
in  to  make  the  mortar  about  as  moist  as  damp  garden- 
earth;  the  gravel  or  stone,  previously  well  wetted,  is 
then  added,  and  the  whole  thoroughly  mixed  by 
repeatedly  turning  over  with  shovels.  The  proportion 
of  water  must  be  so  regulated  that  after  prolonged  and 
vigorous  stamping  the  mass  will  become  elastic  and 
show  a  little  water  on  the  surface.  The  use  of  more 


26      PREPARATION  OF  CONCRETE  FLOORS,  ETC. 

water  is  to  be  avoided,  since  it  makes  the  mass  less 
dense  and  lowers  its  strength.  Too  great  stress  cannot 
be  laid  upon  thorough  and  careful  stamping  of  the  con- 
crete into  place,  since  in  no  other  way  can  great  strength 
and  density  be  obtained. 

With  good  Portland  cement  the  proportion  of  1  part 
cement  and  3  parts  sand,  with  varying  amounts  of 
gravel  or  stone  up  to  9  parts,  will  be  found  suitable; 
for  some  purposes  poorer  mixtures  may  be  used. 

Portland  cement  concrete  finds  many  useful  applica- 
tions in  constructions  both  above  and  below  ground; 
for  example,  in  foundations  of  all  kinds,  sidewalks, 
ceilings,  walls,  arches,  cement  wares,  etc. 

PREPARATION   OF  CONCRETE    FLOORS,    SIDEWALKS,   STEPS 
AND  CEILINGS. 

For  the  construction  of  durable  cement  floors  or  side, 
walks  the  foundation  must  be  suitably  prepared.  For 
outdoor  work  on  yielding  ground  a  porous  layer,  at 
least  10  inches  thick,  of  coarse  gravel  or  slag  should  be 
laid,  well  rammed  down  and  leveled.  For  indoor  work 
on  dry  ground  it  is  sufficient  to  level  the  surface  and 
stamp  it  down  firmly.  Floors  and  sidewalks  are  gen- 
erally  built  in  two  layers;  a  lower  bed  of  concrete  2J 
to  4  inches  thick,  and  a  surface  coat  of  richer  mortar 
of  a  thickness  of  £  to  £  of  an  inch. 

The  concrete  layer  may  be  made  richer  or  poorer 
according  to  the  service  which  the  work  must  undergo. 
For  heavy  duty  a  mixture  of  cement  1,  sand  3  and  gravel 
6  is  recommended.  In  less  important  work  cement  1, 
sand  5  and  gravel  10  will  answer.  A  suitable  mixture 
for  ordinary  requirements  is,  cement  1,  sand  4  and 
gravel  8  or  broken  stone  6. 

The  surface  layer  consists  of  cement  1,  sand  1,  and 


PREPARATION  OF  CONCRETE  FLOORS,  ETC.      27 

must  be  spread  over  the  concrete  before  the  latter  has 
set.  Before  spreading  the  top  layer  the  concrete  shonld 
be  freed  from  loose  material  and  its  surface  roughed 
up.  The  mortar  is  spread  with  a  straight-edge  and 
when  sufficiently  hardened  is  finished  with  a  wooden 
tool.  A  grooved  roller  is  used  to  produce  a  ribbed  sur- 
face, especially  in  side-walk  work. 

When  the  work  is  finished  and  the  cement  is  well  set, 
the  surface  is  carefully  covered  with  a  layer  of  sand  4 
inches  in  thickness.  This  is  moistened  and  kept  in 
place  for  several  weeks  if  possible.  Only  in  this  way 
can  the  formation  of  hair-cracks  be  prevented  and  a 
well  hardened  surface  obtained. 

Cement  expands  and  contracts  with  changes  of  tem- 
perature, in  the  same  way  as  iron,  wood,  sandstone  and 
other  materials.  From  this  cause,  if  the  necessary  care 
has  not  been  taken  in  the  work,  cracks  will  result, 
especially  in  wide  surfaces.  These  may  be  avoided  by 
dividing  the  flooring  into  smaller  blocks,  which  should 
not  exceed  4  to  5  square  yards  in  area,  and  should  be 
separated  by  strips  of  tar  paper  or  by  sand  joints  £  inch 
in  width.  The  joints  in  the  concrete  must  correspond 
with  those  cut  in  the  surface  layer.  The  division  of 
the  work  into  blocks  is  also  to  be  recommended  in  con- 
crete walls  and  curbs. 

One  of  the  most  strikingly  successful  applications  of 
Portland  cement  in  building  is  its  use  for  ceilings  and 
staircases.  Safety  against  fire,  freedom  from  dry-rot, 
quickness  of  construction,  and  cheapness  are  some  of 
the  many  advantages  presented  by  this  type  of  con- 
struction, A  description  of  this  and  other  similar 
applications  of  cement  would,  however,  extend  this 
pamphlet  beyond  desirable  limits.  Reference  must, 
therefore,  be  made  to  special  works  on  this  subject.* 


28         NOTES  ON  CEMENT  WORK  AND  ITS  TREATMENT. 

As  already  stated,  cement  work  must  be  protected 
from  too  rapid  drying  out,  since  from  this  cause  shrink- 
age cracks  and  lack  of  hardness  and  strength  may 
result.  A  certain  amount  of  water  is  absolutely  neces- 
sarjr  for  the  proper  hardening  of  cement. 

In  case  of  sidewalks,  ceilings,  etc.,  the  surface  is  to 
be  kept  covered  with  damp  sand  as  long  as  possible. 
Cement  wares  should  be  kept  under  water,  or  stored  in 
damp  rooms,  free  from  Currents  of  air,  and  frequently 
sprinkled.  Wall-plastering  should  be  kept  covered  as 
long  as  possible  with  wet  sacks  or  cloths.  Cement 
casts  which  are  to  be  exposed  to  weather,  such  as 
statues  and  architectural  ornaments,  must  never  be 
made  of  pure  cement;  a  suitable  proportion  of  sand  is 
necessary,  even  for  the  surface.  By  the  addition  of 
fine,  sharp  sand  the  formation  of  unsightly  hair-cracks 
is  avoided  without  injury  to  the  appearance  of  the 
work.  The  use  of  quick-setting  cement  with  too  little 
sand  and  much  water,  taking  the  objects  too  soon  out 
of  the  moulds,  and  their  delivery  before  they  have 
acquired  the  necessary  hardness,  are  serious  errors. 
Such  treatment  was  formerly  much  more  common  than 
it  is  at  present,  and  has  done  much  to  cause  cement 
wares  to  be  regarded  with  undeserved  suspicion.  Since 
the  introduction  of  more  rational  methods  of  manu- 
facture, castg  in  cement  have  given  full  satisfaction, 
and  owing  to  their  cheapness  are  rapidly  coming  into 
extensive  use.  Architectural  details  for  which  sand- 
stone was  exclusively  used  twenty  years  ago,  are  now 
extensively  cast  in  cement  and  find  application  in  edi- 
fices of  the  most  highly  artistic  character. 


'Portland  cement  und  seine  Anwendungen  im  Bauwesen;  Berlin,  1892. 
n«ment  in  seiner  Verwendung  im  Hochbau;  Liebold,  Halle,  1875. 


CONCLUSION. 


29 


In  conclusion  it  may  be  noted  that  the  remarkable 
properties  of  Portland  cement  make  it  suitable  for  an 
endless  variety  of  uses.  It  is  hoped  that  this  brief 
sketch  may  serve  to  bring  this  valuable  material  into 
more  extensive  notice,  and  to  contribute  to  a  wider 
appreciation  of  its  qualities  and  capabilities. 


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Harmon  S.  Palmer's 

System  of  Hollow  Concrete  Building  Block  Construc- 
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building  blocks  are  rapidly  and  economi- 
cally produced  in  the  H.  S.  Palmer 
Patent     Building    Block 
Machine. 

Forming  a  hollow  wall,  either  plain  rock  faced  or  in  ornamental  designs. 
Produced  cheaper  and  more  durable  than  either  brick  or  stone. 


Residence  of  P.  O.  Caldwell.  Springfield   111. 
Constructed  of  H.  S.  Palmer's  Hollow  Concrete  Building  Block. 


The  Pioneer  of  this  class  of  Machinery  and  owner  of  the 
broad  Basic  patents  for  the  machinery  and  hollow  building 
block  construction  in  all  essential  details.  Now  in  use  in  var- 
ious parts  of  the  U.  S.  and  Canada.  Write  for  catalogue. 

HARMON  S.  PALMER  HOLLOW  CONCRETE 
BUILDING  BLOCK  CO..  Washington,  D.  C. 


YC   13713 


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